Treatment of water and disposal during the production of oil and gas can play a major role in the viability and cost of oil and gas projects. In many locations water is expensive or difficult to obtain. Water may have to be transported to the site or purchased in order to complete a project. Water used during the project is frequently reused as much as possible, and after production the water must be disposed of. In order to recycle or disposal of wastewater, contaminants in the water must be degraded, processed, and/or removed to ensure that the clean environment is not harmed and chemicals are not released.
Hydrates are crystalline solids that can be formed in a fluid whether the fluid is flowing or stationary. Hydrates form crystalline ice-like solids when water under the certain pressures and temperatures in the presence of low molecular weight hydrocarbon gases including methane, ethane, propane, butanes, pentanes, hexanes, H2S, CO2, and other small gases. Although hydrates are most problematic in fluids that are conveyed through pipe, they may form solid under a variety of conditions and block the surface of the pipe, which can lead to catastrophe. Hydrates can also be abrasive and deteriorate the pipe wall. Changes in pressure and temperature may cause hydrates to expand releasing explosive gases and increasing pressures to dangerous levels. There is a need, therefore, for improved and cost effective methods for inhibiting hydrate formation without permanently contaminating water produced or used during the production and transportation of hydrocarbons, including natural gas, crude oil, bitumen, tar sands, and other hydrocarbon sources.
There are two broad techniques to control hydrate formation in hydrocarbons, namely thermodynamic and kinetic inhibitors. Thermodynamic inhibitors include water removal, increasing temperature, decreasing pressure, addition of “antifreeze” to the fluid and combinations of these methods. The kinetic approach generally prevents/delays the smaller hydrocarbon hydrate crystals from agglomerating into larger ones (known in the industry as an anti-agglomerate and abbreviated AA), they also may inhibit, retard and prevent initial hydrocarbon hydrate crystal nucleation or crystal growth (known in the industry as a kinetic hydrate inhibitor and abbreviated KHI). Additionally, films that protect the inside of the pipelines, tubing, valves and such prevent both hydrate crystallization and corrosion of the materials. Thermodynamic inhibitors, kinetic hydrate inhibitors and anti-agglomerate were used to reduce or prevent hydrate formation.
In U.S. Pat. No. 6,646,082 and US2003063998, Ghosh, used oligomeric and polymeric compositions as fluid additives in aqueous systems which are effective corrosion inhibitors over a wide range of pH and render metals passive to repeated attack by oxidants and oxidizing biocides. Dahlman, U.S. Pat. No. 7,435,845, and Leinweber, U.S. Pat. No. 7,615,102, replace hazardous thermodynamic hydrate inhibitors with corrosion inhibitors and gas hydrate inhibitors having improved film persistence and good biodegradability. Talley and Colle, US20080312478, discovered the synergistic effects of the thermodynamic hydrate inhibitors and kinetic hydrate inhibitors are additive and therefore, significantly reduce hydrate formation in a fluid.
Ozonation has been shown to effectively remove surfactants, biological contaminants, and other materials from wastewater for municipal and commercial production services (Klasson et al, 2002). Suzuki and associates (1976 a&b) found P. aeruginosa PEG-K utilized ethylene glycol, diethylene glycol, and triethylene glycol produced by ozone degradation of high molecular PEG followed by treatment with H2O2. Narkis and associates (Narkis and Schneider-Rotel, 1980; Narkis and Schneider-Rotel, 1985; Narkis, et al. 1987) improved biodegradability of non-ionic surfactants caused by ozonation through changes in molecular structure. Delanghe, et al., (1991) reviewed the aqueous ozonation reactions of surfactants including the degree of reaction and ozonation byproduct identity. Homg, et al., (1998) investigated surfactant wastewater treatment by electro-chemical oxidation with or without hydrogen peroxide. Da Pozzo, et al., (2005) described electro-Fenton treatment of a solution containing phosphorus compounds using graphite electrodes. Urbans, (2006) describes the use of peroxide as a water treatment method. Agladze, et al., (2007) optimized cell design and current efficiencies for cathodic reduction of oxygen at gas-diffusion electrodes in membrane cells. Peralta-Hernández, et al., (2009) summarize and analyze the results of electro-Fenton (EF) and photoelectro-Fenton (PEF) methods. Petrucci, et al., (2009) presented enhancement of electro-Fenton treatment, performed by employing a PTFE-bonded gas diffusion cathode. Rosales, et al., (2009) describes the use of the electro-Fenton process to clean soil or clay contaminated by organic compounds. Brillas provides an overview of current oxidation technologies (Oturan and Brillas, 2009; Brillas, 2009; Oturan, et al., 2009). Unfortunately, waste water produced from natural gas, SAGD, LNG, and other hydrocarbon processes contains contaminants not present in other commercial processes. Additionally, KHI materials are becoming more complex, KHI concentrations are increasing, and there is a greater volume of produced water, so systems used to process KHI containing water must work more rapidly on a larger scale than previously available. Processes that involve heating, incineration or other attempts simply produce more waste, use more equipment, or are too expensive to be implemented at the variety of hydrocarbon processing locations around the world under a variety of different environmental conditions.
An efficient KHI removal process is required not only to remove KHI in production and transportations systems today, but that will allow production from more extreme areas, such as deep water and arctic reservoirs where increased pressures and lower temperatures will contribute to hydrate formation. Improved KHI removal will allow higher concentrations of KHI to be used in these more extreme environments. Additionally, KHIs may be used in systems with other more complex contaminants. An efficient and inexpensive method of KHI removal must be developed to remove kinetic hydrate inhibitors from wastewater and process water that allows the water to be either re-injected into the subterranean formation or further processed without producing solid wastes and/or generating toxic by-products that are difficult to dispose of or damaging to the environment.